Secret reproducible bitstrings may be used in various security applications including device identification, authentication, metering, remote activation, and encryption. Physically Unclonable Functions (PUFs) are emerging as an alternative to programming embedded secret keys in read only memories (ROM) and non-volatile memories in integrated circuits (ICs). Physically Unclonable Functions extract entropy from variations in the physical and electrical properties of ICs as a means of generating secret bitstrings. That is, Physically Unclonable Functions may be used to generate unique and random bitstrings for each IC within a population of ICs. Physically Unclonable Functions may incorporate an on-chip infrastructure for measuring and digitizing the corresponding variations.
Some security applications, such as encryption, require precise regeneration of a secret bitstring, possibly under different environmental conditions. This requirement presents challenges for current PUFs, because the entropy source leveraged by a typical PUF may be analog in nature and hence may be significantly impacted by changes in environmental conditions (e.g., temperature and voltage). Moreover, distinguishing subtle differences in the entropy source may be further challenged by measurement noise. Thus, current PUFs may be less than ideal for some security applications.